Abstract
Since the fall armyworm (FAW) Spodoptera frugiperda invaded China, it has coexisted in maize fields with the native cotton bollworm (CBW) Helicoverpa armigera, but the population dynamics and competitive mechanisms between the two pests are not well understood. We evaluated interspecific competition between FAW and CBW by analyzing their bidirectional predation in the laboratory, survival rates when their larvae co-infested the same maize plant, and the population dynamics of both in the same maize field. In the predation tests, FAW and CBW larvae preyed on each other. However, the theoretical maximum predation of sixth-instar FAW larvae preying on first–second-instar CBW larvae was 71.4 and 32.3 individuals, respectively, while that of CBW was 38.5 and 28.6 individuals. The field co-infestation trials showed that the older larvae had a higher survival rate when the two pests co-infested the same maize plants, but young larval survival was higher for FAW than CBW. In the maize field from 2019 to 2021 in southern Yunnan, FAW populations were significantly higher than those of CBW. Our findings suggested that FAW larvae had a predation advantage over CBW, which might be an important reason for its dominance in Chinese maize fields. This result provides a scientific basis for developing a monitoring technology and for the integrated management of pests in invaded habitats of FAW.
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